Medical Microbiology

HaemophilusandPasteurella 303

Epidemiologyandprevention.H.influenzaeisfoundonlyinhumans.The

incidenceofsevereinvasiveinfections(meningitis,sepsis,epiglottitis)inchil-

drenhasbeenreduceddrastically—toaboutonein 10 ofthenumbersseen

previously—sinceavaccinationprogramwasstarted,andwillcontinuetofall

assumingthevaccinationsarecontinued(seevaccinationschedule,p. 3 3).

ImmunizationisachievedwiththeconjugatevaccineHibinwhichthe

capsulepolysaccharideepitope“b”conferringimmunityisconjugatedto

protein.Suchaconjugatevaccinecanbeadministeredasearlyasthefirst

monthoflife.Theimmunesystemdoesnotrespondtopurepolysaccharide

vaccinesuntilabouttheageoftwo,sincepolysaccharidesareT-independent

antigensagainstwhichhardlyanyantibodiesareproducedinthefirsttwo

yearsoflife.Thereisalsonoboosterresponse.Afour-dayregimenofrifam-

picinhasprovedtobeaneffectivechemoprophylactictreatmentfornonvac-

cinatedsmallchildrenwhohavebeenexposedtotheorganism.

HaemophilusducreyiandHaemophilusaegyptius..

H.ducreyiareshort,Gram-negative,nonmotilerodsthataredifficulttocul-

tureandrequirespecialmediums.Thisbacteriumcausesulcusmolle(soft

chancre)atropicalvenerealdiseaseseenrarelyincentralEurope.Theinfec-

tionlocuspresentsasapainful,readilybleedingulceroccurringmainlyinthe

genitalarea.Regionallymphnodesarequiteswollen.Identificationofthe

pathogenbymeansofmicroscopyandculturingareneededtoconfirm

thediagnosis.Therapeuticalternativesincludesulfonamides,streptomycin,

andtetracyclines.

H.aegyptius(possiblyidenticalwithbiovarIIIofHaemophilusinfluen-

zae)causesapurulentconjunctivitisoccurringmainlyinnorthernAfrica,in

particularEgypt.AraisedincidenceofBrazilianpurpuricfever,asystemicin-

fectionwiththisorganism,hasbeenobservedinBrazilinrecentyears.

Pasteurella.............................................

VariousdifferentspeciesbelongingtothegenusPasteurellaoccurinthenor-

malmucosalfloraofanimalsandhumans;somearepathogenicinanimals.

Theirsignificanceashumanpathogensisminor.InfectionsbyPasteurella

multocidaaredescribedhereasexamplesofhumanpasteurelloses.The

bacteriainvadetheorganismthroughbiteorscratchinjuriesorindroplets

duringcontactwithinfectedanimals.Weakenedimmunedefensesmaythen

resultineitherlocalwoundinfectionswithlymphadenitis,subacuteto

chronicinfectionsofthelowerrespiratorytract,orCNSinfections(aftercer-

ebraltraumaorbrainsurgery).Diagnosisisbasedonpathogenidentification.

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Kayser, Medical Microbiology © 2005 Thieme